1. Field of the Invention
This invention relates to a method of forming a circular convergent lens in a plate of transparent mineral material.
2. Prior Art
Watch glasses are often provided with a convergent lens to facilitate the reading of a watch calendar. When the watch glass is of mineral material, the lens is glued to the surface of the glass. This, however, is unsightly, nor can unsticking of the lens be completely avoided. When the watch glass is of organic material, the lens can be embedded within the thickness of the glass. Unfortunately, this type of material is softer and therefore more subject to scratching than mineral materials, such as sapphire, which provide the watch glass with an excellent resistance to abrasion.